MQ Series (also called "MQ", "MQSeries", and "IBM WebSphere MQ") is a messaging solution with a central server. Process A can put a message there, and process B can retrieve the message. If you login onto the prompt of the actual box running MQ - you will see hundreds (if not thousands) processes in memory working on receiving/sending messages. Messages can be huge. The whole system is very reliable. And it supports transactions. Great tool - but expensive (of course). It allows perfect de-coupling between systems. Imagine that system A needs to send something to system B. It puts the message on te MQ server - and continues with whatever it was doing. System B will retrieve the message at its convenience. If system B is turned off for couple hours for maintenance - no problem. Once "B" will go back online - it will retrieve the messages. Nothing will be lost. And system "A" never has to wait for system "B".

Message Broker distributes information and data generated by business events in real time to people, applications, and devices throughout your extended enterprise and beyond.

Provides a smart approach to SOA, extending the reach of your business beyond your firewall by supporting a broad range of multiple transport protocols and data formats

Integrates multiple applications, networks, and device types using a platform-independent based enterprise service bus that lets you conduct business reliably and securely

Increases business agility and flexibility, extending easily to a Federated ESB model, while reducing development costs by separating integration logic from applicationsImproves the flow of information around the business, moving away from hard-coded point-to-point links to more flexible distribution mechanisms such as publish/subscribe and multi-cast

Uses a simple programming model for connectivity and mediation, including a robust set of pre-built mediation function and ways to customize mediations